linux-kernel - Re: [PATCH RFC] input: fix weird issue of synaptics psmouse sync lost after resume

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Date:	Thu, 28 Jun 2012 16:55:18 -0700
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Eric Miao <eric.miao@...onical.com>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-input@...r.kernel.org,
	Ayan George <ayan.george@...onical.com>
Subject: Re: [PATCH RFC] input: fix weird issue of synaptics psmouse sync
 lost after resume

Hi Eric,

On Sun, Jun 24, 2012 at 11:32:38PM +0800, Eric Miao wrote:
> All,
> 
> BugLink: https://bugs.launchpad.net/bugs/717970
> 
> So in summary, the symptom is intermittent key events lost after resume
> on some machines with synaptics touchpad (seems this is synaptics _only_),
> and key events loss is due to serio port reconnect after psmouse sync lost.
> Removing psmouse and inserting it back during the suspend/resume process
> is able to work around the issue, so the difference between psmouse_connect()
> and psmouse_reconnect() is the key to the root cause of this problem.
> 
> After comparing the two different paths, synaptics driver has its own
> implementation of synaptics_reconnect(), and the missing psmouse_probe()
> seems significant, the patch below added psmouse_probe() to the reconnect
> process, and has been verified many times that the issue could not be reliably
> reproduced.
> 
> There are two PS/2 commands in psmouse_probe():
> 
>   1. PSMOUSE_CMD_GETID
>   2. PSMOUSE_CMD_RESET_DIS
> 
> The weird thing is, the PSMOUSE_CMD_GETID seems to be significant, and the
> PSMOUSE_CMD_RESET_DIS is irrelevant to this issue after trying several times.
> Now it's rather difficult to form a sane theory. So this patch is
> really for RFC.

Hmm, murky and unknown to us EC/KBC firmware code and uglies are hidden
there...

I issuing PSMOUSE_CMD_GETID bis fine if it makes some firmware happy and
we probably should do it for all protocols, not only Synaptics. Could
you please try moving calls to psmouse_reset() and psmouse_probe() in
psmouse_reconnect() up, before we check if we have protocol specific
reconnect handler?

Thanks.

-- 
Dmitry
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